Semipurified food containing 1.2 mg of cholesterol/Kcal will be fed to 54 cynomolgus macaques (Macaca fascicularis). At the end of 6 months, a group of 18 animals will be studied for evaluation of atherosclerosis in the aorta and the coronary arteries. The remaining monkeys will be assigned to two groups of 18 animals each and will be fed, during the following 18 months, semipurified food containing 0.34 mg of cholesterol/Kcal with or without 1.2 percent alfalfa saponins. The following variables will be evaluated: survival; general appearance; body weight; plasma lipids; tissue lipids in the aorta; atherosclerosis in the aorta and the coronary arteries; and gross and microscopic pathologic changes in liver, spleen, kidney, adrenals, thyroid, and ovaries.